Process for preparing sand molds



Patented Aug. 7, 1.934

PATENT OFFICE PROCESS FOR PREPARING SAND MOLDS Edward Player, Gibbet Hill, Kenilwoz'.1-., England, assignor, by mesne assignments, to Magnesium Development Corporation,

Delaware a corporation of No Drawing. Application April 24, 1933, Serial No. 667,619. In Germany April 27, 1932 5 Claims.

This invention relates to a process for preparing sand molds for use in the casting of magnesium and magnesium alloys.

It is well known that a comparatively dry sand is required when preparing molds for castingmagnesium and magnesium alloys. This entails the disadvantage that such molds and cores are somewhat friable and liable to damage so that the castings made in such molds frequently exhibit a rather rough surface. A binding medium is therefore desirable which imparts a smooth surface to the molds and cores and also increases the cohesion of the molded sand, so that the manipulation of the core in particular is also facilitated. Such a binding medium must fulfil the requirement of not reacting with the metal, but it need not necessarily act as a specific protective agent against oxidation of the metal, since the known protective substances such as sulphur and boric acid are available for this purpose.

It has now been ascertained inaccordance with the present invention, that certain sugars, namely aldoses and bioses and more particularly glucose, are eminently suitable as such binding media.

In carrying out the invention, these sugars are preferably applied to the surface of the mold by spraying or as a wash in the form of a solution of one part by weight of sugar in about 10 parts by weight of water and the molds are thereupon dried surperficially by fanning them with a blowpipe flame or in anay other suitable way. Grreenv cores can be treated in a similar manner whilst in the case of dried cores the core sand is made up into a core preferably with the. aid 'of the sugar solution, the .molded core being'then dried in the usual manner. However, the sugar solution can also be added to the whole of the sand in the case of green molds and cores.

The binding media hereinbefore specified are not adapted per se to protect magnesium and its alloys against oxidation on casting into green sand molds. On the contrary, it is also necessary to add the known specific protective agents for magnesium and its alloys to the molding sand in the usual manner. Nevertheless by treating the molds and cores with a sugar solution in accordance with the present invention, the cohesive strength of the sand is considerably improved and an excellent smooth surface is imparted to the castings made therein. 5

I claim:

1. A process for preparing sand molds for use in casting magnesium and magnesium alloys, which comprises treating the internal surface of the molds with a solution of at least one sugar of the group consisting of aldoses and bioses and drying said surface.

2. A process for preparing dried cores for use in casting magnesium and magnesium alloys which comprises mixing a solution of at least one sugar of the group consisting of aldoses and bioses with molding sand, forming the core and drying the molded core.

3. A sand mold for use in casting magnesium and magnesium alloys having a smooth cohesive. so internal surface, said surface consisting of molding sand and a binder therefor comprising at least one sugar of the group consisting of aldoses and bioses.

4. A dry sand core for use in casting magnes5 slum and magnesium alloys having a smooth cohesive surface and. a comparatively rigid structure, said core consisting of molding sand and a binder therefor comprising at least one sugar of the group consisting of aldoses and bioses.

5. In a sand mold for casting magnesium and magnesium alloys, an internal mol d surface consisting of molding sand sprayed with a solution comprising at least one sugar of the group consisting of aldoses and bioses.

EDWARD PLAYER. 

